The long-term objectives of this project are to establish the etiology of Kawasaki Syndrome, elucidate the pathogenesis of the disease process, determine the long-term effects of the disease and to devise the optimum form of treatment. Epidemiological, clinical and microbiological investigation of cases during endemic and epidemic periods will continue. There will be a more intensive effort to isolate fastidious pathogens from patients and family members and other close contacts for etiological study. The large collection of serum from patients in all stages of acute and convalescent disease will be used to test etiologic hypothesis as they are formulated by use and others. Immunologic function will be studied in all phases of the disease and in the post-recovery period. The long-term follow-up program is designed to monitor cardiovascular fitness of subjects who have recovered from Kawasaki Syndrome. A major portion of the study will be devoted to investigating in vitro and in vivo models using endothelial and blood mononuclear cell cultures and experimental animals.